This application is based on Japanese Patent Application No. 11-241874 filed Aug. 27, 2000, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an apparatus for controlling an automotive vehicle equipped with a primary drive power source and a secondary or auxiliary drive power source, and more particularly to a drive control apparatus for an all-wheel-drive vehicle wherein one of a front-wheel drive system and a rear-wheel drive system is driven by the primary drive power source while the other drive system is driven by the auxiliary drive power source.
2. Discussion of the Related Art
An automotive vehicle equipped with a primary and a secondary or auxiliary drive power source is known. One example of this type of automotive vehicle is an all-wheel-drive vehicle wherein one of a front-wheel and a rear-wheel drive system is driven by the primary drive power source in the form of an engine (internal combustion engine) while the other drive system is driven by the auxiliary drive power source in the form of an electric or hydraulic motor. For improving the drivability of this type of all-wheel-drive automotive vehicle while maximizing the fuel economy or maintaining desired running characteristics of the vehicle, there is provided a motor drive mode which is selected to apply an output torque of the electric motor to the above-indicated other drive system as an assisting drive torque when it is desired to accelerate the vehicle.
The all-wheel-drive automotive vehicle indicated above can be accelerated even on a frozen, snow-covered or other roadway surface having a low friction coefficient, by driving the auxiliary drive wheels by the auxiliary drive power source (electric motor), when it is desired to accelerate the vehicle in an intermediate degree, during running of the vehicle at a relatively low speed. In this respect, there is known a control apparatus adapted to control the auxiliary drive power source so as to prevent a speed difference of the auxiliary drive wheels, when the vehicle is running straight without deceleration thereof on a roadway surface having a low friction coefficient. An example of this control apparatus is disclosed in JP-A-7-125556.
The known control apparatus for the automotive vehicle having a plurality of drive power sources as described above is not satisfactory in its capability of controlling the auxiliary drive power source, and tends to suffer from drawbacks in terms of the fuel economy and the driving characteristics of the vehicle.
It is therefore an object of the present invention to provide an apparatus for controlling an automotive vehicle equipped with a plurality of drive power source, which apparatus assures satisfactory fuel economy and driving characteristics of the vehicle.
The above object may be achieved according to a first aspect of this invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source and an auxiliary drive power source, comprising; (a) required output determining means for determining a required output of the vehicle which is desired by an operator of the vehicle; and (b) first control means for controlling the auxiliary drive power source such that an assisting drive torque which is generated by the auxiliary drive power source and applied to the vehicle in addition to a primary drive torque generated by the primary drive power source increases with an increase of the required output of the vehicle and such that the auxiliary drive power source is operated for a length of time which decreases with the increase of the required output.
In the apparatus constructed according to the first aspect of the invention described above, the first control means controls the auxiliary drive power source such that the assisting drive torque generated by the auxiliary drive power source increases with an increase of the operator""s desired output of the vehicle and such that the length of time during which the auxiliary drive power source is operated decreases with the increase of the operator""s desired vehicle output. Thus, the auxiliary drive power source is suitably controlled. For example, the required vehicle output desired by the vehicle operator is represented by the operating angle or amount of an accelerator pedal. The first control means permits an increase of the total drive force of the vehicle corresponding to to the operating amount of the accelerator pedal, with the assisting drive torque generated by the auxiliary drive power source, so that a further increase in the operating amount of the accelerator pedal is prevented, and the required amount of fuel consumption by the vehicle is reduced.
The control apparatus is preferably applicable to an automotive vehicle wherein the primary drive power source, which may be an internal combustion engine, is used to drive one of a front-wheel drive system and a rear-wheel drive system, while the auxiliary drive power source, which may be an electric motor, is used to drive the other of the front- and rear-wheel drive systems. In this case, both of the front- and rear-wheel drive systems are driven while the auxiliary drive power source is operated, so that the vehicle can be suitably driven or accelerated with a suitable total drive force, even on a frozen or snow-covered surface or any other roadway surface having a comparatively low friction coefficient.
The control apparatus constructed according to a first preferred form of the above-indicated first aspect of the present invention further comprises assisting drive torque compensating means for compensating the assisting drive torque as determined by the first control means, so as to determine a ratio of the assisting drive torque as compensated by the assisting drive torque compensating means to the primary drive torque, so that fuel economy of the internal combustion engine is maximized.
The control apparatus constructed according to a second preferred form of the first aspect of this invention further comprises: roadway surface friction coefficient determining means for determining whether a friction coefficient of a roadway surface on which the vehicle lies is lower than a predetermined threshold; and second control means operable when the roadway surface friction coefficient determining means has determined that the friction coefficient of the roadway surface is lower than the predetermined threshold, the second control means reducing an output of the primary drive power source and operating the auxiliary drive power source, and wherein the first control means operates the auxiliary drive power source such that the assisting drive torque increases with the increase of the required output of the vehicle and such that the length of time of the auxiliary drive power source decreases with the increase of the required output, when the roadway surface friction coefficient determining means has determined that the friction coefficient is not lower than the predetermined threshold.
In the control apparatus constructed according to the second preferred form of the invention, the first control means is operated when the friction coefficient of the roadway surface is comparatively high, to operate the auxiliary drive power source such that the assisting drive torque generated by the auxiliary drive power source increases as the vehicle operator""s desired vehicle output is increased, and such that the length of operation of the auxiliary drive power source decreases as the desired vehicle output is increased. Accordingly, the drivability of the vehicle is further improved, making it possible to prevent a further increase of the operating amount of the accelerator pedal and reduce the required amount of fuel consumption by the vehicle.
The control apparatus constructed according to a third preferred form of the first aspect of the invention further comprises third control means operable when the roadway surface friction coefficient determining means has determined that the friction coefficient is not lower than the predetermined threshold, the third control means reducing an output of the primary drive power source with an increase in the assisting drive torque generated by the auxiliary drive power source.
In the control apparatus constructed according to the third preferred form of the first aspect of the invention, the third control means is adapted to reduce the output of the primary drive power source with an increase in the assisting drive torque generated by the auxiliary drive power source, when the roadway surface friction coefficient determining means has determined that the friction coefficient of the roadway surface is comparatively high. Accordingly, the output of the primary drive power source is reduced or limited according to the assisting drive torque generated by the auxiliary drive power source, even when the roadway surface is a dry surface having a comparatively high friction coefficient, so that the fuel consumption of the vehicle can be further reduced.
The above indicated above may also be achieved according to a second aspect of the present invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source and an auxiliary drive power source, comprising: assisting drive torque control means for operating the primary drive power source to generate a primary drive torque on the basis of a required output of the vehicle which is desired by an operator of the vehicle, and simultaneously operating the auxiliary drive power source such that an assisting drive torque which is generated by the auxiliary drive power source and applied to the vehicle in addition to said primary drive torque is a predetermined percentage of the primary drive torque; and fourth control means operable after initiation of an operation of the auxiliary drive power source, for controlling the auxiliary drive power source so as to optimize a percentage of the assisting drive torque with respect to the primary drive torque, on the basis of an energy consuming state of the primary drive power source.
In the control apparatus constructed according to the above second aspect of the invention, the assisting drive torque control means operates the primary drive power source on the basis of the operator""s desired vehicle output and simultaneously operates the auxiliary drive power source such that the assisting drive torque generated by the auxiliary drive power source is a predetermined percentage or ratio of the primary drive torque, and the fourth control means controls the operation of the auxiliary drive power source so as to optimize the percentage of the assisting drive torque with respect to the primary drive torque, on the basis of the state of energy consumption of the primary drive power source after initiation of the operation of the auxiliary drive power source. Accordingly, the energy consumption by the primary drive power source is reduced.
The object indicated above may also be achieved according to a third aspect of the present invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source and an auxiliary drive power source, comprising; fifth control means for operating the auxiliary drive power source while limiting an output of the primary drive power source when a required output of the vehicle which is desired by an operator of the vehicle is smaller than a predetermined threshold and when a power mode in which the vehicle is driven with high drivability is not selected by the operator, the fifth control means reducing an amount of limitation of the output of the primary drive power source while controlling the auxiliary drive power source, when the required output of the vehicle is not smaller than the predetermined threshold and when the power mode is selected by the operator, such that an assisting drive torque which is generated by the auxiliary drive power source and applied to the vehicle in addition to a primary drive power source generated by the primary drive power source is made larger than that when the required output is smaller than the predetermined threshold and when the power mode is not selected, and such that the auxiliary drive power source is operated for a shorter length of time than when the required output is smaller than the predetermined threshold and when the power mode is not selected.
In the control apparatus constructed according to the third aspect of this invention, the fifth control means operates the auxiliary drive power source while limiting the output of the primary drive power source when the operator""s desired vehicle output is relatively small and when the power mode is not selected by the operator, and reduces the amount of limitation of the output of the primary drive power source while controlling the auxiliary drive power source, when the desired vehicle output is relatively large and when the power mode is selected, such that the assisting drive torque generated by the auxiliary drive power source is made larger than in the above-indicated vehicle condition, and such that the auxiliary drive power source is operated for a shorter length of time than in the above-indicated vehicle condition. Thus, the manner of operation of the auxiliary drive power source is changed depending upon when the power mode is selected by the vehicle operator or not, so that the assisting drive torque generated by the auxiliary drive power source is optimized, and the fuel consumption by the primary drive power source is reduced. Further, the amount of limitation of the output of the primary drive power source is reduced when the power mode is selected by the operator, so that the drivability of the vehicle is improved.
The object indicated above may also be achieved according to a fourth aspect of the present invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source, an energy storing means for storing an energy, an auxiliary drive power source operated with the energy stored in the energy storing means, and energy generating means operated by the primary drive power source, for generating an energy, comprising: required output determining means for determining whether a required output of the vehicle which is desired by an operator of the vehicle is larger than a predetermined threshold; and sixth control means for supplying the energy from the energy storing means to the auxiliary drive power source such that an assisting drive torque which is generated by the auxiliary drive power source and applied to the vehicle in addition to a primary drive torque generated by the primary drive power source is relatively small, while the required output of the vehicle determined by the required output determining means is not larger than the predetermined threshold, and wherein while the required output of the vehicle determined by the required output determining means is larger than the predetermined threshold, the sixth control means supplies not only the energy stored in the energy storing means but also the energy generated by the energy generating means to the auxiliary drive power source, such that the assisting drive torque generated by the auxiliary drive power source is larger than while the required output is not larger than the predetermined threshold and such that the auxiliary drive power source is operated for a length of time shorter than while the required output is not larger than the predetermined threshold.
In the control apparatus constructed according to the above fourth aspect of the invention, the sixth control means operates in two different manners depending upon whether the vehicle output desired by the operator is larger than the predetermined threshold or not. While the operator""s desired vehicle output is not larger than the threshold, the sixth control means supplies the energy from the energy storing means to the auxiliary drive power source such that the assisting drive torque generated by the auxiliary drive power source is relatively small. While the operator""s desired vehicle output is larger than the threshold, the sixth control means supplies not only the energy stored in the energy storing means but also the energy generated by the energy generating means operated by the primary drive power source, to the auxiliary drive power source, such that the assisting drive torque is larger than while the desired vehicle output is not larger than the threshold and such that the length of time of operation of the auxiliary drive power source is shorter than while the desired vehicle output is not larger than the threshold. Accordingly, the operation of the auxiliary drive power source is maximized, and the drivability of the vehicle is improved when the vehicle load is large or the desired vehicle drive power is comparatively large.
The object indicated above may also be achieved according to a fifth aspect of the present invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source, an energy storing means for storing an energy, an auxiliary drive power source operated with the energy stored in the energy storing means, energy generating means operated by the primary drive power source, for generating an energy, and a transmission operatively connected to the primary drive power source, comprising: stored energy amount determining means for determining whether an amount of energy stored in the energy storing means is smaller than a predetermined threshold; and seventh control means operable when the stored energy amount determining means has determined that the amount of energy stored in the energy storing means is smaller than the predetermined threshold, for supplying the energy from the energy generating means to the auxiliary drive power source, and increasing a speed ratio of the transmission so as to increase a drive force of the vehicle.
In the control apparatus constructed according to the above fifth aspect of the invention, the seventh control means is operated when the amount of energy stored in the energy storing means is insufficient or smaller than the predetermined threshold. The seventh control means supplies the energy from the energy generating means operated by the primary drive power source, to the auxiliary drive power source, and increases the speed ratio of the transmission so as to increase the vehicle drive force. As a result of an increase in the speed ratio of the transmission, the output of the auxiliary drive power source is optimized even while the energy amount stored in the energy storing means is reduced.
The object indicated above may also be achieved according to a sixth aspect of this invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source, an energy storing means for storing an energy, an auxiliary drive power source operated with the energy stored in the energy storing means, and energy generating means operated by the primary drive power source, for generating an energy, comprising:
eighth control means for operating said auxiliary drive power source with an energy suppled from the energy generating means, in a selected one of a first mode and a second mode, the eighth control means operating the auxiliary drive power source in the first mode such that a moment of initiation of an operation of the auxiliary drive power source with the energy supplied from the energy storing means is retarded by a predetermined time after a moment at which an operation performed by an operator of the vehicle to increase an output of the vehicle is initiated, the eighth control means operating the auxiliary drive power source in the second mode such that the operation of the auxiliary drive power source with the energy supplied from the energy storing means is initiated at the moment at which the operation performed by the operator is initiated.
In the control apparatus constructed according to the sixth aspect of the invention, the eighth control means is operated, upon supplying of the energy from the energy generating means to the auxiliary drive power source, in a selected one of the first and second modes. In the first mode, the moment of initiation of the operation of the auxiliary drive power source with the energy supplied from the energy generating means is retarded by the predetermined time after the moment of an operation performed by the vehicle operator (e.g., an operation of an accelerator pedal) to increase the vehicle output is initiated. In the second mode, the operation of the auxiliary drive power source is initiated at the same time when the operation to increase the vehicle output is initiated. For instance, the first mode is selected when the power mode for driving the vehicle with high drivability is selected, while the second mode is selected when the power mode is not selected.
The object indicated above may also be achieved according to a seventh aspect of the present invention, which provides an apparatus for controlling an automotive vehicle having a primary drive power source, an energy storing means for storing an energy, an auxiliary drive power source operated with the energy stored in the energy storing means, and energy generating means operated by the primary drive power source, for generating an energy, comprising: ninth control means operable when an operation to accelerate the vehicle is performed by an operator of the vehicle, for first initiating a supply of an energy from the energy generating means to the auxiliary drive power source, and then initiating a supply of an energy from the energy storing means to the auxiliary drive power source when a predetermined time has passed after a moment of initiation of the supply of the energy from the energy generating means to the auxiliary drive power source.
In the control apparatus constructed to the above seventh aspect of the invention, the ninth control means is operated when the operator""s operation to accelerate the vehicle is performed. The ninth control means first initiates the supply of the energy from the energy generating means operated by the primary drive power source, to the auxiliary drive power source, and then initiates the supply of the energy from the energy storing means to the auxiliary drive power source when the predetermined time has passed after the moment of initiation of the supply of the energy from the energy generating means to the auxiliary drive power source. Accordingly, the acceleration of the vehicle can be increased when the vehicle operator performs an operation to accelerate the vehicle. Further, the vehicle can be accelerated for a sufficiently long time.